Qual Life Res (2012) 21:299–307 DOI 10.1007/s11136-011-9942-3
Differences in quality of life of hemodialysis patients between dialysis centers Albert H. A. Mazairac • Muriel P. C. Grooteman • Peter J. Blankestijn • E. Lars Penne • Neelke C. van der Weerd • Claire H. den Hoedt • Marinus A. van den Dorpel • Erik Buskens • Menso J. Nube´ • Piet M. ter Wee G. Ardine de Wit • Michiel L. Bots
•
Accepted: 19 May 2011 / Published online: 2 June 2011 Ó The Author(s) 2011. This article is published with open access at Springerlink.com
Abstract Purpose Hemodialysis patients undergo frequent and long visits to the clinic to receive adequate dialysis treatment, medical guidance, and support. This may affect health-related quality of life (HRQOL). Although HRQOL is a very important management aspect in hemodialysis patients, there is a paucity of information on the differences in HRQOL between centers. We set out to assess the differences in HRQOL of hemodialysis patients between dialysis centers and explore which modifiable center characteristics could explain possible differences. Methods This cross-sectional study evaluated 570 hemodialysis patients from 24 Dutch dialysis centers. HRQOL was measured with the Kidney Disease Quality Of Life-Short Form (KDQOL-SF). Results After adjustment for differences in case-mix, three HRQOL domains differed between dialysis centers:
the physical composite score (PCS, P = 0.01), quality of social interaction (P = 0.04), and dialysis staff encouragement (P = 0.001). These center differences had a range of 11–21 points on a scale of 0–100, depending on the domain. Two center characteristics showed a clinical relevant relation with patients’ HRQOL: dieticians’ fulltimeequivalent and the type of dialysis center. Conclusion This study showed that clinical relevant differences exist between dialysis centers in multiple HRQOL domains. This is especially remarkable as hemodialysis is a highly standardized therapy. Keywords Quality of life Center differences Hemodialysis Dialysis staff encouragement Abbreviations HRQOL Health-related quality of life KDQOL-SF Kidney Disease Quality Of Life-Short Form
This study is conducted on behalf of the CONTRAST investigators. See ‘‘Appendix’’ for list of CONTRAST investigators. A. H. A. Mazairac P. J. Blankestijn E. Lars Penne N. C. van der Weerd C. H. den Hoedt Department of Nephrology, University Medical Center Utrecht, Utrecht, The Netherlands
E. Buskens MTA Unit, Department of Epidemiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
M. P. C. Grooteman E. Lars Penne N. C. van der Weerd M. J. Nube´ P. M. ter Wee Department of Nephrology, VU Medical Center, Amsterdam, The Netherlands
G. A. de Wit M. L. Bots (&) Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, PO Box 85500, 3508 GA Utrecht, The Netherlands e-mail:
[email protected]
M. P. C. Grooteman M. J. Nube´ P. M. ter Wee Institute for Cardiovascular Research VU Medical Center (ICaR-VU), VU Medical Center, Amsterdam, The Netherlands
G. A. de Wit National Institute for Public Health and the Environment, Bilthoven, The Netherlands
C. H. den Hoedt M. A. van den Dorpel Department of Internal Medicine, Maasstad Hospital, Rotterdam, The Netherlands
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SF-36 CONTRAST BMI eGFR PCS MCS SD FTE
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Short Form 36 Convective transport study Body mass index Estimated glomerular filtration rate Physical component summary Mental component summary Standard deviation Fulltime equivalent
Introduction Health-related quality of life (HRQOL) can be defined as the perceived health status in physical, social, and mental domains [1]. Attention to and focus on HRQOL is illustrated by the growing number of studies on HRQOL [2]. Different clinical variables that contribute to HRQOL have been evaluated [3], but a paucity of information remains on the potential important role of the clinic itself. The HRQOL of hemodialysis patients is hard-pressed. They not only face the chronic health problems of renal failure but also the intrusiveness of a time-consuming therapy. As a result, the HRQOL of hemodialysis patients is lower than in patients with congestive heart failure, chronic lung disease, or cancer [4]. For in-center hemodialysis patients, frequent and long visits to the clinic are required in order to receive adequate dialysis treatment, medical guidance, and support. Does this entwinement lead to differences between dialysis centers in patients’ HRQOL? And if so, can modifiable center characteristics be identified that are related with HRQOL? Relevant differences between dialysis centers have been shown for mortality [5–9] and intermediate outcomes such as dialysis adequacy [10], hematocrit [11], and vascular access [12]. It was our aim to assess differences in HRQOL between dialysis centers using the Kidney Disease Quality of Life-Short Form (KDQOL-SF), which combines the well-known, generic Short Form 36 (SF-36) with a kidney disease-specific assessment of HRQOL [13]. Our second aim was to explore center characteristics that were related to HRQOL.
in CONTRAST. CONTRAST is a randomized controlled trial (ISRCTN38365125) comparing the effects of low-flux hemodialysis with online hemodiafiltration on all-cause mortality and cardiovascular events, as described elsewhere [14]. In short, patients were eligible if treated with hemodialysis 2 or 3 times a week, for at least 2 months, with a minimum dialysis urea Kt/V C 1.2, and able to understand the study procedures. Exclusion criteria were age \18 years, treatment by hemodiafiltration or high-flux hemodialysis in the 6 months preceding randomization, severe incompliance defined as non-adherence to the dialysis prescription, a life expectancy \3 months due to causes other than kidney disease, and participation in another clinical trial. The study was conducted in accordance with the Declaration of Helsinki and approved by the medical ethics review boards of all participating hospitals. Written informed consent was obtained from all patients prior to enrollment. Data collection
Materials and methods
At baseline, standardized forms were used to collect demographic, clinical and laboratory data. Demographic data included age, gender, race, and educational level. Clinical characteristics included cause of kidney failure, diabetic state and previous cardiovascular disease, vascular access, hemodialysis dose (single pool Kt/V urea), time on renal replacement therapy in years, treatment time in hours, blood pressure, body mass index (BMI), dialysis frequency, residual kidney function, and smoking habit (yes/no). Laboratory values were measured using standard techniques. The second generation Daugirdas formula was used to calculate single pool Kt/V for urea [15]. Residual kidney function was expressed as estimated glomerular filtration rate (eGFR), calculated as the mean of creatinine and urea clearance and adjusted for body surface area [16]. Center characteristics included the number of dialysis patients per center, nurse, and dialysis session; the proportion of available patients enrolled in CONTRAST; frequency of patient—physician (assistant) contacts; the fulltimeequivalent (FTE) of nephrologists, nurses, social workers, and dieticians; availability of exercise during dialysis (yes/ no); dialysis modalities offered (peritoneal, home, and nocturnal dialysis); university hospital (yes/no) and regional satellite unit (yes/no).
Patients and study design
Kidney Disease Quality of Life-Short Form
This cross-sectional study used baseline data of the Convective Transport Study (CONTRAST) [14]. The analyses are based on 570 participating hemodialysis patients from 24 dialysis centers in The Netherlands. Centers were only included in this analysis if at least 10 patients participated
HRQOL was assessed with the validated KDQOL-SF version 1.3 (http://gim.med.ucla.edu/kdqol/downloads/ -download.html) [13, 17]. It covers different domains to face the multidimensional nature of HRQOL. The KDQOL-SF can be split in a generic part and a disease-
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Table 1 The Kidney Disease Quality of Life-Short Form (KDQOL-SF): the kidney disease-specific scales Domains
Meaning Low
High
Symptom/problem list
Extremely bothered by dialysis-related symptoms such as muscle cramps, pruritus, anorexia, and/or access problems
Not at all bothered
Effect of kidney disease on daily life
Extremely bothered by fluid and dietary restriction, by an inability to travel and dependency on doctors
Not at all bothered
Burden of kidney disease
Extremely bothered by the time consumed by dialysis, its intrusiveness and degree burden on family
Not at all bothered
Work status
Unemployed due to health
Employed, health not an issue
Cognitive function
Affected all of the time by inability to concentrate, confused with poor reaction time
Not at all affected
Quality of social interaction
Continual irritation and failure to get along with people with virtual isolation
No problem, socially interactive
Sexual function
Experiencing severe problems with enjoyment and arousal
No problems
Sleep
Very poor sleep with day time somnolence
No problem with sleep
Social support
Very dissatisfied
Satisfied with level of social support
Dialysis staff encouragement
High perceived encouragement and support
Low perceived encouragement and support
Overall health
Rates health as worst possible
Rates health as best possible
Patient satisfaction
Very poor
The best
Modified from Carmichael et al. [37]
specific part. First, the generic part is formed by the SF-36 version 1. The domains of the SF-36 can be summarized in two summary scores, one for physical functioning (physical component summary—PCS) and one for mental functioning (mental component summary—MCS). These summaries are constructed so that a score of 50 represents the mean of the general United States population with a standard deviation of 10 [18]. Second, the disease-specific part of the KDQOL-SF consists of 44 kidney disease-targeted questions. The responses to these items are condensed in 12 domains (Table 1). These domains have a score from 0 to 100, with higher scores indicating the absence of problems. A difference of 5 points has been proposed to be clinical relevant with regard to individual domains, and a difference of 3 points with regard to the composite scores [18, 19].
variables. Process variables are characteristics that may be influenced by patient factors as well as dialysis staff modifications e.g. Kt/V, type of vascular access, hemoglobin, albumin, and phosphate levels [20]. The relation between center characteristics and HRQOL was evaluated independent of case-mix covariates. Multilevel linear models or logistic regression was applied, depending on the distribution of the residuals: parametric or non-parametric. To facilitate logistic regression, non-parametrically distributed domains were dichotomized using the median as cut-off value. We used single regression analysis to account for missing values [21]. The median extent of missing was 5% in the HRQOL domains analyzed, 2% of case-mix covariates, 0% of center variables, and 0% of process variables. Results were considered statistically significant if P \ 0.05 (twotailed comparison). All analyses were conducted using SPSS 18 (SPSS Inc. Headquarters, Chicago, Illinois, USA).
Data analysis Patient characteristics were reported as means with standard deviation (SD), medians with interquartile ranges, or proportions when appropriate. First, differences in HRQOL between dialysis centers were assessed, while adjusting for case-mix covariates and the variation in the proportion of enrolled patients. Case-mix covariates were age, gender, race, educational status, history of cardiovascular disease, diabetes, eGFR, and time on renal replacement therapy in years. Second, additional adjustments were made for process
Results Patient characteristics The characteristics of the 570 hemodialysis patients are summarized in Table 2. The mean age was 64 ± 14 (SD) years, 62% of the patients were male, and 93% dialyzed 3 times per week.
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Table 2 Patient characteristics (N = 570)
Table 3 Center characteristics (N = 24 centers)
Demographic
Number of patients treated
Age (years)
64 ± 14
Total
Gender (% male)
62
On HD or HDF
81 (64–125)
Caucasian (%)
86
Per dialysis shift
20 (15–25)
High educational statusa (%)
24
Per nurse
Clinical parameters Dialysis vintage (years)
1.9 (1.0–4.2)
Dialysis frequency (%)
109 (85–155)
2–2.5
5 (21%)
3–3.5
17 (71%)
4–4.5
2 (8%)
29 per week
6
Setting
39 per week
93
General hospital
49 per week
1
University hospital
4 (17%)
Session duration (hours)
4.0 (3.5–4.0)
Regional satellite unit
2 (8%)
Offered dialysis modalities
18 (75%)
spKt/V urea
1.4 ± 0.2
eGFR (mL/min/1.73 m2)b
2.8 (1.2–5.2)
Peritoneal dialysis
23 (96%)
Vascular access (% fistula) Body mass index (kg/m2), after dialysis
84 25 ± 4
Home dialysis Nocturnal dialysis
14 (58%) 13 (54%)
Systolic blood pressure (mmHg), before dialysis
142 ± 20
Diastolic blood pressure (mmHg), before dialysis
73 ± 11
Nephrologist
Current smoker (%)
21
Nurse
30 (26–34)
Diabetes mellitus (%)
20
Social worker
1.6 (1.3–1.8)
History of cardiovascular disease (%)
42
Dietician
0.9 (0.6–1.2)
Hemoglobin (mmol/L)
7.3 ± 0.8
Albumin (g/L)
36 ± 5
Calcium (mmol/L) Phosphate (mmol/L)
FTE dialysis staff per 100 patients 2.6 (2.1–3.2)
Patient–physician (assistant) contacts per month 29
3 (13%)
2.3 ± 0.2
49
18 (75%)
1.6 ± 0.5
[49
3 (13%)
Mean ± SD or median (interquartile range)
Availability of physical exercise during dialysis
20 (83%)
To convert hemoglobin in mmol/L to g/dL divide by 0.62; albumin in g/L to g/dL, divide by 10; calcium in mmol/L to mg/dL, divide by 0.25; phosphate in mmol/L to mg/dL, divide by 0.323
Center medians (interquartile ranges) or percentages HD hemodialysis, HDF hemodiafiltration, FTE fulltime-equivalent
eGFR estimated glomerular filtration rate a
high educational status: college or university level
b
In 278 patients with diuresis C100 mL/24 h (52%)
Dialysis center characteristics Table 3 depicts the center characteristics (N = 24 centers). The median number of dialysis patients that was treated in a participating center was 109 (interquartile range 85–155) of which 81 (64–125) were on HD or HDF. Twenty-seven percent (17–35) of these patients were enrolled for the current study. Based on the median FTE per patient, there were 2.6 (2.1–3.2) nephrologists per 100 dialysis patients. Fourteen centers (58%) offered home dialysis, and 4 (17%) were part of a university hospital.
interaction (P = 0.04), and dialysis staff encouragement (P = 0.001). These results did not change if the differences in HRQOL between centers were furthermore adjusted for process variables. The differences in HRQOL had a maximum range of 11–21 points. Center characteristics and quality of life Two center characteristics showed a clinical relevant relation with patients’ HRQOL (Table 5): dieticians’ FTE and the type of center. Dieticians’ FTE per patient was positively related to perceived dialysis staff encouragement. Multiple HRQOL domains were better in satellite units and worse in university hospitals.
Quality of life differences between dialysis centers Discussion Three HRQOL domains differed between the dialysis centers when the variation in case-mix covariates and proportion of enrolled patients was taken into account (Table 4, Fig. 1): the PCS (P = 0.01), quality of social
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This study showed clinical relevant differences in the HRQOL of hemodialysis patients between dialysis centers in three domains: the PCS, quality of social interaction, and
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Table 4 Differences in quality of life between dialysis centers (N = 24 centers) Score
P-value Crude
Adjusted Case-mix
Case-mix ? process variables
Generic domains (SF-36) Physical component summary (PCS)
40 ± 4
0.002
0.01
0.01
Mental component summary (MCS) Kidney disease-specific domains
51 ± 3
0.01
0.20
0.27
Symptom/problem list
80 ± 4
0.06
0.68
0.94
Effects of kidney disease on daily life
73 ± 5
0.35
0.59
0.48
Burden of kidney disease
47 ± 8
0.01
0.46
0.54
Work status
0 (0–0)
0.71
0.67
0.58
Cognitive function
80 ± 6
0.01
0.11
0.19
Quality of social interaction
83 ± 5
0.04
0.04
0.02
Sleep
62 ± 7
0.08
0.20
0.42
Social support
78 ± 7
0.44
0.33
0.18
Dialysis staff encouragement
78 ± 7
